Redundant functions of the SLC5A transporters Rumpel Kumpel and Bumpel in ensheathing glial cells

Neuronal processing is energy demanding, and relies on sugar metabolism as an energy source. To provide a constant metabolite supply neurons and glial cells express many glucose and lactate transporters of the solute carrier (SLC) 5A family. Here we dissect the partially redundant functions of three highly related glia specific Drosophila genes encoding SLC5A proteins, Rumpel, Bumpel and Kumpel. While knockdown of rumpel causes several behavioral phenotypes, they are less prominent in rumpel mutants. bumpel and kumpel mutants are viable and fertile, lacking discernible phenotypes. However, in bumpel kumpel double mutants and to an even greater extent in rumpel bumpel kumpel triple mutants oogenesis is disrupted at the onset of the vitollegenic phase. This indicates at least partially redundant functions between these genes. Rescue experiments exploring this effect indicate that oogenesis can be affected by CNS glial cells. Moreover, expression of heterologous mammalian SLC5A transporter proteins, with known transport properties, suggest that Bumpel and/or Kumpel transport glucose or lactate. Overall, our results imply a redundancy in SLC5A nutrient sensing functions in Drosophila glial cells, affecting ovarian development and behavior.